For common cellular applications where a given site has three sectors, each serviced by one antenna, each antenna usually has 65 degree azimuth Half Power Beamwidth (HPBW). Six sector cells may be employed at such sites to increase system capacity. Antennas with 33 degree and 45 degree HPBW are the most common for 6 sector applications. However, replacing three antennas with six antennas (each of which is 2 times wider than a common 65 degree antenna) is not a compact and low cost solution.
Dual-beam (or multi-beam antennas) may be used to reduce number of antennas on the tower. One key aspect of a multi-beam antenna is the beam forming network (BFN). An example of a known dual-beam antenna from prior art may be found in Encyclopedia for RF and Microwave engineering, 2005 John Wiley and Sons, pp. 335-339. In the known dual beam antenna, a two beam by two column (2×2) BFN is used. The main drawback of this prior art antenna is high levels of side and backlobes (about −10 dB), which is not acceptable for modern systems due high interference. Another drawback is poor coverage: more than 50% of radiated power is wasted out of the desired two 60 degree sectors.
Another dual-beam prior art solution may be found in U.S. Pat. No. 8,237,619. This example includes a three column array. However, it also has very high sidelobes (about −9 dB) and relatively narrow operational band (1.7-2.1 GHz). In modern telecommunication systems it is desirable to include the LTE 2.6 GHz band, and a cover a bandwidth of 1.69-2.69 GHz, which is about 2.5 times wider bandwidth than in known solutions.
Another dual-beam prior art solution is U.S. Patent Pub. No. 2011/0205119, which is incorporated by reference. In the '119 application, improved azimuth suppression and wideband operation is achieved by including different antenna sub-arrays into an antenna array. For example, the antenna may include a two beam by three column array and a two beam by two column array. However, bandwidth is also limited for this prior art solution.
Consequently, there is a need to provide an improved antenna, with more consistent HPBW across a wider frequency bandwidth, better azimuth sidelobe suppression, with better coverage of desired sector and less interference with other sectors.